The present invention relates to an igniting device for protective devices in vehicles having a pyro-electric igniting element which contains a fusible conductor which can be heated by current flow and an inflammable material which is in thermal contact with the fusible conductor, and having at least two igniting connections.
In motor vehicles, pyro-electric igniting elements are provided for triggering protective devices, such as, for example, belt-tightening or airbag systems. These igniting elements contain low-resistance fusible wire links and a chemical inflammable material which encloses or embeds the wire links. If sufficient current flows through the fusible wire, it heats to a temperature at which the inflammable material is ignited.
These igniting elements have the disadvantage that they can be ignited even with the application of relatively low voltages. For instance, ignition can occur by circuit checkers accidentally slipping on the feed wires incorrectly or by applying the vehicle voltage in the course of negligent manipulation. In the event of an undesired triggering of an airbag, the consequence can be damage to property or an accident.
It is therefore an object of the present invention to provide a simple igniting device which does not exhibit these disadvantages and offers high inherent safety with respect to unwanted ignition triggering.
This and other objects are achieved in an igniting device for protective devices in vehicles constructed in accordance with the present invention, which comprises a pyro-electric igniting element which contains a fusible conductor that can be heated by current flow and an inflammable material which is in thermal contact with the fusible conductor. The igniting device has at least two igniting connections coupled to the pyro-electric igniting element, an electrically controllable switch having a contact gap and a control input, this contact gap being connected in series with the fusible conductor, and an electronic lock. The electronic lock has an input and an output, the electronic lock output being coupled to the control input of the switch, which is actuated by the electronic lock to close the contact gap when an unlocking signal is received at the electronic lock input and at least by the time an igniting signal provided for activating the fusible conductor has been applied to the igniting device.
The actual pyro-electric igniting element, the switching component which is connected in series with the igniting element, and the electronic lock for applying current to the igniting element can all be combined in an integral component according to an embodiment of the present invention.
Current can only be applied to the pyro-electric igniting element if, when an igniting signal is present at the igniting device having these characteristics, an additional unlocking signal was already present and "opened" the electronic lock.
The device according to the invention thus offers very high safety with respect to mistriggering, since two signals required for the triggering of the igniting element must be present at the igniting device according to the invention in order to make its operation possible at all.
In certain embodiments of the invention, the time characteristic of the unlocking signal is coded in a manner effecting the opening of the electronic lock. The unlocking signal can be supplied to the igniting device independently of the igniting signal, line-conducted or not line-conducted or together with the igniting signal.
For opening the electronic lock, the unlocking signal can contain, for example, a code in the form of a certain pulse sequence (digital code). The electronic lock can also respond to a code frequency.
To supply both the electronic lock and the switching element with operating power, at least one, and preferably both igniting lines can be used. In addition, the reactive inflammable substance can be directly connected to a silicon chip implementing the electronic lock. In this case, for example, a bonding wire which is present in any case and may be specially formed out and/or run can also be provided as fusible wire link.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.